Semiconductor laser device and a method for producing the same

Abstract

A semiconductor laser device is provided which is constituted by semiconductor materials so as to emit laser light from a cavity end facet, the laser light being excited in a waveguide within an active layer sandwiched between a pair of cladding layers, wherein a window layer made of a semiconductor material having a band gap greater than that of the active layer is formed on the cavity end facet from which the laser light is emitted, so as to have a thickness sufficient to prevent local generation of crystal defects by lattice mismatching between the semiconductor material of the window layer and the semiconductor materials at the cavity end facet. There is also provided a method for producing such a semiconductor laser device with high efficiency.

What is claimed is: 
     
       1. In a semiconductor laser device which is constituted by semiconductor materials so as to emit laser light from a cavity end facet, the laser light being excited in a waveguide within an active layer sandwiched between a pair of cladding layers, wherein a window layer made of a semiconductor material having a band gap greater than that of the active layer is formed on the cavity end facet from which the laser light is emitted, so as to have a sufficient thickness of 0.2 nm to 3 μm to prevent local generation of crystal defects by lattice mismatching between the semiconductor material of the window layer and the semiconductor materials at the cavity end facet. 
     
     
       2. In a semiconductor laser device according to claim 1, wherein the window layer has a band gap greater than that of the active layer by at least 300 meV. 
     
     
       3. In a semiconductor laser device according to claim 1, wherein the band gap of the window layer is greater than that of the cladding layers. 
     
     
       4. In a semiconductor laser device according to claim 1, wherein the window layer is covered with an insulating film so that the reflectivity of at least one of the cavity end facets becomes 5 to 20%. 
     
     
       5. In a semiconductor laser device according to claim 1, wherein the waveguide within the active layer has a uniform width. 
     
     
       6. In a semiconductor laser device according to claim 1, wherein the width of the waveguide within the active layer is smaller in the cavity portions near the end facets and greater in the center portion other than these end portions. 
     
     
       7. In a semiconductor laser device according to claim 1, wherein the semiconductor materials are AlGaAs. 
     
     
       8. In a semiconductor laser device according to claim 1, wherein the semiconductor materials are InGaAlP. 
     
     
       9. In a semiconductor laser device according to claim 1, wherein the semiconductor materials are a mixture of AlGaAs and InGaAlP. 
     
     
       10. In a semiconductor laser device according to claim 1, wherein a protective layer is formed on the surface of the window layer, the protective layer having a band gap different from that of the window layer. 
     
     
       11. In a semiconductor laser device according to claim 1, wherein a protective layer which is a sulfur-containing film is formed on the surface of the window layer. 
     
     
       12. In a semiconductor laser device according to claim 10 or 11, wherein the protective layer is covered with an insulating film so that the reflectivity of at least one of the cavity end facets becomes 5 to 20%. 
     
     
       13. A method for producing a semiconductor laser device which emits laser light from an end facet thereof and not only has an active layer for laser oscillation but also has a semiconductor layer with a band gap greater than that of the active layer, which is formed on the end facet, comprising the steps of: cleaving a semiconductor laser wafer to form a plurality of bar-shaped wafers having a width which is substantially equivalent to a cavity length; and   fixing the bar-shaped wafers in a supporting jig and then introducing it into a growth chamber for vapor phase epitaxy to grow the semiconductor layer at least on the cleavage planes of the bar-shaped wafers.   
     
     
       14. A method according to claim 13, wherein the bar-shaped wafers are fixed by a fixing jig together with the supporting jig.